1. Technical Field
The present invention relates to a radio network controller and a channel assignment method by the apparatus and in particular relates to a method of channel switching in a wideband-CDMA (W-CDMA) system.
2. Background Art
In recent years, a code division multiple access (CDMA) communication system has been under rapid development. In addition to current main service based on voice and still images, commercializing service of a wideband CDMA system (W-CDMA) has also been started. Under such a situation, by the 3rd Generation Partnership Project (3GPP, http://www.3gpp.org/) that is a 3rd generation mobile communication system standardizing group, various specifications based on the W-CDMA system have been drawn up in order to realize a system in which it is possible to provide high-quality service.
The W-CDMA system mainly includes user equipments, base stations that terminate wireless sections, radio network controllers that control the base stations, and an exchange that manages the radio network controllers. As transmission lines between the base stations and the user equipments, wireless transmission lines are used, so there is a limitation on usable resources (frequencies). Further, the mobile communication system is required to be capable of placing as many user equipments as possible under a communicable state. Therefore, in the W-CDMA system, effective use of the limited wireless resources is achieved by using different channels that are individual channels and common channels having mutually different characteristics.
In the W-CDMA system, assignment of the individual channels and the common channels to the user equipments is changed as appropriate in accordance with communication rates desired by the user equipments and the amounts of data actually transferred between the radio network controllers and the user equipments so that the wireless resources are used with efficiency. This changing of the assignment of the individual channels and the common channels is referred to as “channel switching”.
When consideration is given to the effective use of the wireless resources, it is required that this channel switching be carried out in a real-time manner in accordance with the data transfer rates between the radio network controllers and the user equipments. Therefore, capability of carrying out of the channel switching in short cycles and shortening of times taken by the channel switching as much as possible lead to an increase in communication quality.    [Patent document 1] JP 2001-505018 A    [Patent document 2] JP 2000-278327 A